Total hip replacement is one of the most successful procedures in all of medicine. In the vast majority of cases, total hip replacement enables patients to live more active lives without debilitating hip pain. Over time, a hip replacement can fail for a variety of reasons. When this occurs, a revision operation may be necessary to remove some or all of the parts of the original prosthesis and replace them with new ones, a procedure known as revision total hip replacement. Although both procedures have the same goals - to relieve pain and improve function and quality of life - revision surgery is different than primary total hip replacement, as it is a longer, more complex procedure. Revision surgery requires extensive planning, as well as the use of specialized implants and tools, in order to achieve a good result. Optimal outcomes are also more likely to be achieved by a surgeon with specific subspecialty training and experience in this difficult procedure.
Overview
During primary total hip replacement, the damaged hip joint is replaced with an implant, or prosthesis, made of metal and plastic or ceramic components. Although most total hip replacements are very successful, with satisfaction outcomes of about 95%, over time problems such as implant wear and loosening may require a revision procedure to replace the original components, and sometimes the bone around the hip also needs to be rebuilt with augments (metal pieces that substitute for missing bone) or bone graft. Damage to the remaining bone usually makes it difficult to use standard primary total hip implants for revision hip replacement. In most cases, specialized implants are needed that are designed to compensate for the damaged bone and soft tissues, and which provide for extra mechanical support.
Indications for Revision Total Hip Replacement
Revision hip replacement surgery may be recommended if one or more of the following conditions are present:
Implant Loosening and Wear
In order for a total hip replacement to function properly, an implant must remain firmly attached to the bone. During the initial surgery, the hip replacement components were either cemented into place or were "press fit" into the bone to allow bone to grow onto them. Sometimes, however, bone may fail to grow onto press-fit components. In addition, cemented or press-fit components that were once firmly fixed to the bone may eventually loosen, resulting in a painful hip. The cause of loosening may not always clear, but repetitive high-impact activities, excessive body weight, and wear of the plastic liner between the ball and the metal cup are factors that may contribute. Irrespective of the cause, definite implant loosening can be seen on serial imaging (X-ray) studies over time, and it is important to bring all investigative studies for assessment by A/Prof Woodgate
In addition, patients who are younger when they undergo the initial hip replacement may "outlive" the life expectancy of their artificial hip. For these patients, there is a higher long-term risk that revision surgery will be needed due to loosening or wear (although the minimal wear with ceramic articulations increases the likely longevity of the implant).
In metal-on-plastic cases, tiny particles that wear off the cup's plastic liner accumulate around the hip joint and are attacked by the body's immune system, which can then also lead to erosion of the healthy bone around the implant, leading to a condition called osteolysis making the implant loose or unstable. Fortunately, plastics have improved greatly over the years, so plastic wear and osteolysis occur less frequently today than they did with earlier generations of implants.
Infection
Infection is a potential complication of any surgical procedure, including total hip replacement, with a reported incidence of approximately 1%. Infection occurs when bacteria attach in and around the surface of the prosthesis. Infection may occur while you are in the hospital or after you go home, and may even occur years later.
If a total hip replacement becomes infected, it can be painful and the implant may begin to lose its attachment to the bone. Even if the implant remains properly fixed to the bone, there may still be pain, instability, and drainage from the infection, which may communicate with the skin surface (this is known as a sinus). Bacteria cannot be easily eliminated from a joint replacement with antibiotics alone, and revision surgery is usually necessary.
Revision surgery for infection can be managed in a number of ways, depending on the type or aggressiveness of the bacteria, the duration of infection, time since the original (index primary) hip replacement, general condition of the patient (particularly with regard to co-morbid conditions, which includes the ability to tolerate the anaesthesia for prolonged or multiple surgical procedures), and patient preferences and expectations. Options can include:
- Debridement, Antibiotics, and Implant Retention (DAIR) - In this procedure, the hip can be washed out and the inflamed lining removed to decrease the number of bacteria, the femoral head and the acetabular (cup) liner components can be exchanged, and the metal implants (femoral stem and acetabular (cup) shell can be left in place, and the patient is maintained on longer-term antibiotic treatment (perhaps involving a combination antibiotics).
- One-stage Revision Surgery – In this technique, the infected implants are completely removed, the hip is thoroughly debrided and washed out to remove all signs of infection. A separate set of clean sterile instruments is then used to reimplant the new hip components.
- Two-staged Revision Surgery - In other cases, the implants are completely removed, along with all infected material to treat the infection in the first stage surgery, and a temporary antibiotic-loaded cement spacer may be placed in the hip. This spacer delivers high dose therapy locally within the hip joint cavity, and is supplemented with intravenous and/or oral antibiotic treatment for several weeks (typically 6 weeks). When the infection has been cleared, the second stage surgery is performed to remove the antibiotic spacer and insert the final new hip implants. In general, two-stage surgery tends to yield a higher chance of curing the infection, but is associated with a longer recovery, as well as the need for two separate surgical procedures.
An antibiotic spacer placed in the hip joint during the first stage of treatment for joint replacement infection.
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4. Rarely, due to the patient being unfit for any surgery or prolonged anaesthesia, antibiotic suppression alone is used.
Recurrent Dislocation / Instability
A hip replacement has a ball-and-socket structure like that of your natural hip, and to work well, the ball must remain centrally positioned inside the socket. Trauma or certain hip positions can sometimes cause the ball to become dislodged from the socket, and is called a "hip dislocation." After a first hip replacement dislocation, it must be determined whether the cause was patient factors, implant factors or surgical factors. The first dislocation should be reduced in the operating theatre to allow determination of the stability and reason for the episode. If recurrent hip dislocations occur, you may need revision surgery to alter the mechanics or alignment of the hip joint, possibly involving insertion a special implant designed to prevent dislocations.
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(Left) Dislocation after primary hip replacement. (Right) The revision implant is designed with a ring mechanism that locks the femoral head (ball) into the socket to prevent dislocation (this is one of many options available and each situation is treated individually).
Fractures (Periprosthetic)
A periprosthetic fracture is a broken bone that occurs around or adjacent to the components of a joint replacement. These fractures are most often the result of a fall, and usually require revision surgery, particularly if the implants are loosened by the trauma. In determining the extent of the revision needed, several factors are considered including the quality of the remaining bone, the type and location of the fracture, the type of the original implant (can fixation be achieved maintaining the implant), and whether the implant is loose. Occasionally, the implant itself can break. When the bone is shattered or weakened from osteoporosis, the damaged section of bone may need to be completely replaced with a larger bone-replacing revision component (also known as an endoprosthesis, megaprosthesis, or tumour prosthesis – even if no tumour is present).
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(Left) This patient has a periprosthetic fracture of the femur (thighbone). (Right) The same fracture after treatment with revision surgery and a new femoral stem and multiple cables.
Leg Length Inequality
It is possible to change the length of the leg during hip replacement surgery, especially when using modular implants to reconstruct the anatomy as accurately as possible. This should not really occur if a leg length device is utilised intra-operatively to measure any changes. Whilst A/Prof Woodgate uses a leg length device (which also measure offset) in ALL primary hip cases, this is by no means universal, and in fact one of the commonest causes for litigation after hip replacement surgery in the USA is related to unexpected changes in leg length. Many patients may tolerate being slightly shorter in the operated hip /leg, as this can be easily compensated through a small insert hidden in the shoe. It is more of an issue for over-lengthening, as then any change may need to be done to what may have been a normal leg/side. It is surprising on occasions how much inequality has been created inadvertently by surgeons not using any measuring/calibration device. Patients with significant and symptomatic inequality may be candidates for revision surgery.
A sometimes confounding factor, however, can occur in patients who develop pelvic obliquity (tilt) on a background of degenerative spinal disease, or in patients who have abductor (gluteal) tendon tears around the hip replacement as this may give the appearance of a leg length inequality, when in fact there may be no real change. These cases are managed on an individual basis.
Change in Offset and Abductor (Gluteal) Tendon Dysfunction
It is also possible to change the offset (distance between the centre of the femoral head and the line of the centre of the femur) during hip replacement surgery. If the offset is significantly decreased, this can lead to relative weakening of the abductor (gluteal) muscles on the side of the hip, resulting in a “lurching” gait pattern. If the offset is increased, this will lead to over-tightening of the abductor muscle group, which can result in relative tilting of the pelvis and the leg may feel long. More chronically, increased offset can lead to trochanteric syndrome (also known as trochanteric bursitis), and it a worst case scenario, the overload on the tendons can lead to tears developing at the insertion to the greater trochanter of the femur (the bony prominence at the top of the thigh bone), which then results in a markedly “lurching” gait and a feeling also of leg length inequality. Most modern leg length devices used in primary hip replacement surgery can also measure offset to avoid this complication. If, however, it has occurred, consideration may be need for revision surgery to correct the offset.
The abductor tendons can spontaneously tear, more commonly in females. If this is noted on any pre-operative MRI scans done, or seen intra-operatively, it should be repaired at the time of the primary surgery, thought this will by necessity modify the post-operative rehab programme. If a tear develops after hip replacement surgery, or perhaps had been missed during the initial surgery, it may be possible just to repair the tendons, provided the offset had not been significantly altered by the hip replacement implant.
Adverse Reaction to Metallic Debris (ARMD) and Allergy to Metal
The metals used in artificial hip implants can break down or wear over time, causing tiny particles to be released from the surface of the device into the space around the implant. This is more common with "metal-on-metal" articulating implants, that is, both the ball and socket components are made of metal. In some patients, sensitivity to the metal ions in these particles can result in damage to the bone and soft tissues around the hip and lead to the need for revision surgery. The individual response to these metals is extremely variable if or when it does occur, and it often does not correspond to the level of metal ions that may be measured by blood testing. Even more interestingly, if a reaction does occur, it is usually either predominantly involving bone erosion (osteolysis) and can occur around the acetabular socket, the femoral stem, or both, or it can more effect the soft tissues and tendons around the hip replacement causing the formation of a large bursa (fluid and debris filled sac) or secondary tendon tearing/rupture, or both. However, it is more unusual to see both bone erosion and tendon changes in the same patient. These reactions can also occur early or much later after the hip surgery, and there is no predictive test. Xrays will be needed for investigation, and are often combined with CT and MRI scans to delineate the extent of involvement. If bone or tendon damage is seen, especially with change or elevation in blood metal levels, revision surgery should be undertaken.
In very rare cases, a patient allergy to the metal used in implants may cause pain around the site of the implant. There is no definitive agreement among doctors regarding metal allergy in this setting, however, and more studies are needed. Often a suspicion may be seen if a patient reports inability to wear certain jewellery or watches.
Evaluation for Revision Total Hip Replacement
When a patient presents with a total hip replacement that is not performing well, due to pain, instability, stiffness, limp, or other reason, it is important to obtain as much information as possible to determine the cause prior to undertaking under revision surgery.
A/Prof Woodgate will take a full history and perform a physical examination, particularly concentrating on the hip but also looking for other potential sources of symptoms (e.g. referred pain from the knee, back or pelvis).
Imaging tests will be needed including plain X-rays, which are used to identify the primary hip prosthetic components, alignment or changes with the length or offset, any features suggestive of loosening or bone loss (osteolysis), possible instability or subluxation/dislocation, fractures or soft tissue swelling. Supplemental imaging studies may subsequently be ordered including CT scans (which can more closely assess bone quality, implant orientation and positioning) and MRI scans (usually requires a special sequencing software programme known as metal artefact reduction sequencing or MARS) which may demonstrate more clearly any soft tissue inflammation, features of infection, subtle fractures, tendon tears (particularly in the abductor group of muscles), formation of any bursal collections, and very rarely tumours. Nuclear medicine bone scans are often combined with white cell labelled scans or marrow scans if there is an index of suspicion that infection is the cause of hip symptoms.
Laboratory investigations are also required, not only as part of the general medical assessment but also to look for infection with blood tests showing elevation of the inflammatory markers (particularly the ESR and CRP). Metal ion levels will usually be assessed if there has been a metal-on-metal articulation previously. A hip aspiration is occasionally performed to assess the type of cells in the hip fluid (elevated differential white cell count in infection) as well as sending the fluid to microbiology to culture any potential organisms (although cultures on aspirates often only identify the organism in about 60-65% of cases).
If a cause of the hip symptoms is clearly determined, and surgery is to proceed, A/Prof Woodgate will also obtain the original information from your previous surgical procedure, including copies of the old operation report and the hip implant inventory list. It is important for you to provide the information as to when and where the previous surgery was performed to expedite this process.
Risks and Complications
As with any major surgical procedure, there are risks associated with revision total hip replacement surgery. The procedure is longer and more complex than primary total hip replacement, and has a greater risk of complications. Before your surgery, A/Prof Woodgate will discuss the risks with you and will take specific measures to help avoid any potential complications.
The possible risks and complications of revision total knee surgery include:
- Poor wound healing
- Infection in the wound or the new prosthesis – While the reported rate of infection in primary hip replacement is 0.5-1.5%, the rate of deep infection in revision hip surgery is significantly higher, in the range of 4-10%. In view of this, antibiotic therapy will often continue for longer post-surgery to diminish this risk.
- Bleeding
- Blood clots (DVT) in the leg veins
- Pulmonary embolism—a blood clot in the lungs
- Dislocation or instability
- Leg length inequality
- Damage to nerves or blood vessels
- Bone fracture during surgery
- Tendon damage/injuries
- Prosthetic failure/wear
- Implant loosening
- Reduced range of motion or stiffness in the hip
- Formation of excessive new bone around the hip (heterotopic ossification)
- Medical problems such as heart attack, lung complications, or stroke.
Surgical Procedure
You will be admitted to the hospital on the day of surgery. Revision total hip replacement is more complex and takes longer to perform than primary total hip replacement. In most cases, the surgery takes from 2-4 hours, but can take even longer of there is a need for major bony reconstruction.
The surgery is performed under spinal and general anaesthesia/sedation. Following routine cleaning of the skin with antiseptic solution, sterile drapes are applied. The line of the incision made may incorporate the wound made during your primary total hip replacement, though the wound incision may be longer than the original to allow the old components to be removed. The actual internal approach to expose the hip joint and implants, as well as to plan for reconstruction, will be chosen on an individual basis by A/Prof Woodgate. Specimens for microbiology and histopathology are taken from multiple soft tissues sites around the hip to exclude infection (the histopathology can involve frozen section analysis which is completed in about 15 minutes, and with accuracy of about 98% with regards to diagnosis or exclusion of infection). The metal and/or ceramic/plastic parts of the primary hip prosthesis are assessed to determine which parts have become worn or loose or shifted out of position, and this should confirm the pre-operative diagnosis. The tendons around the hip are also inspected to determine if repairs will be needed. Prior to hip implant dislocation, a leg length device measurement will be taken. The original implant(s) are very carefully removed to preserve as much bone as possible. If cement had been used in the primary total hip replacement, this is also removed, but this can be a lengthy and tedious part of the procedure. Special approaches are also available to aid in implant removal and subsequent reconstruction. Assuming infection has been excluded by the pre-operative and intra-operative tests, preparation of the bone surfaces for the revision implant is undertaken. In some cases, there may be significant bone loss around the hip, and if this occurs, metal augments or platform blocks can be added to make up for the bony deficit, or bone graft material may be used to help rebuild the hip (acetabular and/or femoral reconstruction). The graft may come from your own bone (autograft) or from a donor (allograft). Finally, the specialized revision implant components are inserted and secured (these can either be cemented or uncemented) along with any other supplemental fixation such as screws, cables, wires or plates. The hip is relocated, any surrounding soft tissues that are damaged are repaired, and the hip is carefully assessed for motion, stability and balance, and measurements of leg length and offset are confirmed. A drain may be placed in the hip to collect any fluid or blood that may remain after surgery. A Painbuster catheter and device will also be inserted into the hip joint to deliver local anaesthetic (it will run for about 48 hours post surgery). The wound is then closed in layers, and sterile pressure dressings are applied. After surgery, the anaesthetic is reversed and you will be transferred to the recovery room, where you will remain for several hours for close monitoring. After your condition is confirmed to be stable, you will be taken to your hospital room.
Due to the significant variability and complexity of revision hip surgery, A/Prof Woodgate uses a number of different hip implants for this reconstructive procedure. The commonest revision total hip replacement would involve the use of the Global acetabular cup (Global Orthopaedic Technology), and the S-ROM modular femoral stem ( Depuy/Synthes). In cases of severe femoral loss, the bone can be replaced by a large metal component or endoprosthesis (also known as a tumour prosthesis), and A/Prof Woodgate currently uses the LPS implants ( Depuy/Synthes) in this situation.
Post-Operative Care and Recovery
Most patients will stay in hospital for 3-7 days post hip revision surgery, though this may vary particularly if there has been major abductor or trochanteric reconstruction, which often is managed initially with a few days of traction in bed. Recovery from revision surgery is typically slower than after the primary hip replacement, though the type of in-hospital care is very similar, including:
- Pain Management – As well as the Painbuster catheter delivering local anaesthetic for approximately 48 hours, you will also be given regular Paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), and for the first 48-72 hours, a PCA (Patient Controlled Analgesia) pump to deliver on-demand opioids (narcotic). After the drip is removed, the PCA will cease and oral narcotics (such as Targin and Endone) will be added.
- Physical Therapy – This is initially supervised exercises with the physiotherapist, as well as your own self-initiated exercises, with the goal of restoring range of motion and strength. Weight-bearing restrictions may be necessary if there has been a major reconstruction or tendon repair.
- Blood Clot Prevention – This includes graduated short compression (TED) stockings, inflatable calf compressors, and blood thinning agents (such as Clexane injections). Foot and ankle movements are also encouraged to increase blood flow in the leg.
- Infection Prevention – Intravenous antibiotics will usually be given for 48 hours in the post-operative period, sometimes followed by oral antibiotics.
A significant number of patients subsequently elect to be transferred to an inpatient rehabilitation hospital to undertake early supervised physiotherapy and hydrotherapy. This is particularly useful for those patients who live alone.
Other patients choose to go directly home, but it is often safer to arrange for a friend, family member or caregiver to provide some help at home in the early stages. An outpatient programme of exercises and hydrotherapy can still be arranged prior to your initial hospital discharge. You will continue to wear the short compression (TED) stockings for 6 weeks, thinning (Clexane) injections are typically used for a total of 4 weeks from surgery (although those with higher risk may need a longer treatment phase), ice is used regularly to control swelling, a pain management plan is created for each patient prior to discharge, and advice is provided for planned suture removal. The use of the triangular (abduction) pillow also continues for 6 weeks.
Most importantly, if any concerns develop, particularly if there are any developing signs of blood clots or infection, you MUST contact A/Prof Woodgate as soon as possible.